1. Field of the Invention
The present invention relates to an outboard motor and, more particularly, an improvement in a cover structure and a drain structure in an engine space of the outboard motor.
2. Background Information
A body of an outboard motor is conventionally formed from an aluminum alloy. In recent years, however, a demand has grown for a new engine-housing cover made from resin for reduction in weight and cost. A combination of a synthetic resin lower cover divided generally into left and right halves and a synthetic resin upper cover demountably mounted on the lower cover, for example, has been put to practical use.
In the cover, the engine space is made as large as possible for easy engine mounting operation and maintenance. Resin molded parts, however, have smaller rigidity as compared to aluminum alloy parts. It is especially required to provide a resin lower-half cover supporting a demountable cover with sufficient rigidity.
For securing the rigidity of a resin cover, a cover with a ribbed configuration is presented, for example, in Japanese Patent Laid Open Publication No. HEI-6-234393. This cover structure avoids the influence of sink marks due to ribs on the shell member consisting of resin parts.
However, the above cover, whose ribbed configuration needs to be thickened, requires verification by trial that sink marks do not appear on the exterior of the resin cover, taking time to be commercialized and having disadvantages in quantity production and cost.
When the ribs of the above ribbed resin cover cooperate with another body part to be fitted thereto to constitute a bottom portion constituting part of a partition wall for the engine space, the existence of webs requires another consideration to the withdrawal direction from the mold or prevents grooves from being made much deep in view of the draft for the ribs, resulting in a limited degree of freedom in design.
Thus desired is an outboard motor with an external cover such as an engine cover of a resin cover which has secured rigidity without being made thick, facilitating the production, and having a cost benefit.
An outboard motor allowing for maximum prevention of entering of water from the outside into the engine space which houses the engine is also known. This outboard motor is configured to quickly drain water entering from the outside.
For drainage, a small opening has been conventionally provided, for example. Provision of such a small opening, however, contrarily leads to entering of water from outside.
A “Drain Device for Outboard Motor” having a drain opening for discharging water entered into the engine space, and provided with a check valve for preventing entry of water from the drain opening into the engine space has been presented, for example (Japanese Patent Laid-Open Publication No. SHO-55-83696).
This drain device, however, has a cost disadvantage due to the provision of the check valve. A drain portion formed by cutting off part of a resilient sealing member fitted onto a flange provided below the engine has a vertical passage structure with a simple opening shape. Entry of water from the outside is thus prevented only by the shutting-off function of the check valve.
In this context, an outboard motor capable of preventing extraneous water from entering the engine space of the outboard motor and of smoothly draining entered extraneous water with a simple structure is desired.